Energy is a glossary indicating an ability to work and is a physical term, such as heat, electricity, and force. In the present age, representative examples of this energy include a variety of energies, such as electric energy, thermal power energy, hydraulic energy, and thermal energy.
In the case of electric energy, the most basic method of transferring the energy is to transfer the energy through a conductor through which an electric current can flow.
Another method of transferring electric energy includes a method using an electric field in order to generate power. This method corresponds to technology for transmitting power from one side to the other side by a primary coil and a secondary coil using induced electromotive force that is induced by a magnetic field and an electric field. This method is basically used in a power plant.
As yet another method, a method of transmitting energy wirelessly includes radio wave technology for transmitting a signal having specific power on air. This radio wave technology is widely used in wireless communication methods, but is not an efficient energy transmission method.
Meanwhile, a new method of transferring power was developed in Massachusetts Institute of Technology (MIT) in 2007. The new method relates to technology for transmitting energy wirelessly. In this technology, wireless energy is transmitted through mutual resonance based on magnetic field resonance using a magnetic resonant body having two same frequencies unlike in the existing antenna. In the method disclosed by MIT, the magnetic resonant body has a helical structure and a resonant frequency of 10 MHz. The structural helical resonant body of the resonant body is 600 mm in diameter, 5.25 turns in helical, 6 mm in line thickness, i.e., diameter, and 200 mm in a total helical thickness, and a single feeding loop of a signal is 250 mm.
The method developed by MIT is problematic in that the size and resonant frequency are not suitable for being applied to actual products. That is, the resonant body for wireless power transmission is too bulky, and the resonant frequency is most sensitive to the human body. In order to transmit wireless power in an actual product, it is preferred that the resonant frequency be 10 MHz or less. However, the size of a resonance structure is a function of the resonant frequency. That is, in order to lower the resonant frequency used in the method developed by MIT, that is, in order to lower the resonant frequency, there is a problem in that the size in the resonant structure is increased.